Several different methods of extruding thermal plastics are well known in the industry, including methods for both cold and hot feed extrusion. By using extrusion technologies such as these, an infinite number of extrusion profiles that can be extruded depending on the shape and contour of the particular die used in the extrusion process. The four most common extrusion profiles are tubing, channel, cord and bulb seals.
Finished extruded material can be made into continuous rolls of varying length, generally referred to in the industry as extrudate. The length of the extrudate roll is typically specified from a customer's stock order. Alternatively, the finished extruded material can be formed to make individual parts that often resemble an endless loop or ring, typically referred to by those skilled in the art and hereinafter as a gasket, a continuous gasket, or an endless gasket. An endless gasket is formed by welding the opposite ends of a single piece of extruded material together to create an endless loop shape. The end products whether originating from extrudate or an endless gasket can include residential weather seals, automotive weatherseals and gap fillers, major appliance seals, construction seals, architectural glazing seals, large diameter pipe seals, and various seals used in equipment or machinery.
During the manufacturing of an endless gasket, extruded material is frequently cut to length for a particular application and then welded together end-to-end to form an infinite number of shapes and sizes. The most common endless gaskets form a rectangular or circular pattern.
It is not uncommon for a break to occur in the extrudate for any number of reasons, including fatigue or stress on the extrusion, depletion of raw materials making up the compound, machine break-down, and/or operator neglect during the manufacturing process. Since the extrudate is sent in rolls conforming to a customer's specified length, a splice is frequently needed in order to make the material, once again, continuous, which avoids the creation of scrap because the extrusion length without out a splice becomes too short to fill the customer's order. A splice may also be needed in the endless gasket product in order to connect two ends of a single extruded piece of material in order to form a continuous ring.
Therefore, a joining process is needed in order to unite opposite ends of a single article to make an endless gasket or to unite separate pieces of extruded material in order to form an extrudate. For example, heat may be applied through a heating element during a welding operation at the extruded material ends. During the joining process a splice results between the ends of two separate extrusions or the two ends of the single extrusion. After the welding operation, the resulting splice can leave an undesirable seam or flash, which is not part of the finished product. This flash is particularly undesirable in extruded profiles that perform a sealing function. In addition, the flash generates extra cost to the product by requiring an additional deflashing operation, either manually by an operator or by a mechanical trimming operation. Trimming the flash can also propagate tears, thereby weakening the welded joint.
The cost associated with trimming and removing flash material from an extruded product can be significant because of the additional operations and/or labor. This cost can be compounded in scrap that is produced when the flash removal results in trimming important parts of the finished product through operator error or machine overshoot in mechanical trimming operations.